Effects Of Dietary α-ketoglutarate Supplementation On Growth Performance, Serum Biochemical Indices And Intestinal Development Of Songpu Mirror Carp(Cyprinus Carpio)

This experiment was aimed to study the effects of α-ketoglutarate (AKG)supplementation in different protein level diets on growth performance, serumbiochemical indices, intestinal morphology of Songpu mirror carp. There were4proteinlevels (28%,31%,34%and37%, respectively) and3AKG concentrations (0,0.75%and1.50%, respectively) in the experiment. A total of720Songpu mirror carp with anaverage body weight of (61.28±3.40) g were divided into12groups with3replicatesper group and20fish per replicate. The experiment lasted for8weeks. The resultsshowed as follows:(1) Weight gain rate (WGR) were significantly increased, hepatosomatic index(HSI), visceralsomatic index (VSI), efficiency ratio (PER) and feed conversion ratio(FCR) of Songpu mirror carp were reduced by protein levels(P<0.05). The interactionof the protein level and AKG concentration had significant effects on whole fish ash(P<0.05), and had no significant effects on other body composition indices and growthperformance indices (P>0.05). Under the each protein level, AKG supplementationshowed a tendency to increase WGR and protein PER and decrease FCR of Songpumirror carp, but the differences were not significant (P>0.05) except the WGR under the34%protein level (P<0.05).(2) Protein levels had significant effects on serum alanine aminotransferase (ALT),cholesterol (TCHO), creatinine (CREA), total bilirubin (TBIL) and indirect bilirubin(IBIL) contents (P<0.05). With protein levels increasing serum ALT, TCHO, CREATBIL and IBIL contents were significantly decreased. AKG concentrations hadsignificant effects on serum ALT, aspartate aminotranaferase (AST) activity,triglyceride (TG) contents. The interaction of the protein level and AKG concentrationhad significant effects on serum UA and TG contents (P<0.05), and had no significanteffects on other serum biochemical indices (P>0.05). Under the28%protein level, theserum TG content in1.50%AKG group was significantly lower than that in control group (P<0.05), but there was no significant difference between0.75%and1.50%AKGgroups (P>0.05). Under the31%protein level, the serum albumin (ALB) content andALT activity in1.50%AKG group were significantly higher than those in0.75%AKGand control groups (P<0.05); the serum UA and TG contents in0.75%and1.50%AKGgroup were significantly lower than those in control group (P<0.05). Under the34%protein level, the serum total protein (TP) and TG contents in0.75%AKG group weresignificantly higher than those in control group (P<0.05). Under the37%protein level,the serum ALT activity and UA content in1.50%AKG group were significantly higherthan those in0.75%AKG and control groups (P<0.05); the serum AST activity in0.75%and1.50%AKG groups were significantly higher than that in control group (P<0.05).AKG supplementation had no significant effects on serum globulin (GLB), TCHO andCREA contents and alkaline phosphatase (AKP) activity under the each protein level(P>0.05).(3) AKG can significantly improved the protease activity in foregut and hindgut(P<0.05). Protein levels can significantly reduce fold height of foregut and midgut andamylase in hindgut (P<0.05). The interaction of the protein level and AKGconcentration had significant effects on protease and amylase activity in foregut(P<0.05). Under28%protein level, fold height of midgut in AKG groups weresignificantly higher than control group (P<0.05). Under34%protein level, proteaseactivity in foregut in0.75%AKG group was significantly higher than control group(P<0.05).(4) AKG could significantly improve glutamine synthetase (GS) activity andalkaline phosphatase activity(AKP) in midgut (P<0.05), Protein levels had significanteffects on GS activity and Na+,K+-ATPase activity in foregut and midgut and AKPactivity in midgut (P<0.05), The interaction of protein level and AKG concentration hadsignificant effect on GS activity in midgut and hindgut and Na+,K+-ATPase activity inhindgut (P<0.05), and had no significant effect on other indices (P>0.05). Under28%protein level, GS activity in midgut and hindgut in1.50%AKG group weresignificantly higher than control group (P<0.05). Under31%protein level, GS activityin hindgut in0.75%AKG group was significantly higher than that in control group(P<0.05). Under37%protein level, GS activity in midgut in1.50%AKG group wassignificantly higher than control group (P<0.05).(5) Protein levels had significant effects on superoxide dismutase(SOD) activityin foregut (P<0.05). AKG concentrations had no significant effects on SOD, malondialdehyde(MDA) and reduced glutathione(GSH) of Songpu mirror carp. The interaction of proteinlevel and AKG concentrations had significant effect on SOD activity in foregut and MDA content in hindgut (P<0.05).It is concluded that appropriate supplementation of AKG in diets has a positiveeffect on the protein, intestine development, protease activity of Songpu mirror carp.